1. Field of the Invention
The present invention relates to a steering control system for a vehicle, more particularly, to a front-wheel steering control system for correcting a steering angle of front wheels by an electric motor or the like.
The present application claims priority from Japanese Application Nos. 2005-196722 and 2005-204748, the disclosures of which are incorporated herein by reference.
2. Description of the Related Prior Art
Conventionally, there have been proposed many techniques for correcting a steering angle of front wheels of a vehicle being input by a driver. For example, Japanese Patent Application Laid-Open No. 2004-168166 discloses a steering control apparatus with a variable steering gear ratio in which a differential factor depending on a steering angular velocity is shifted from a positive range to a negative range in proportion to an increase of a vehicle speed. Moreover, a steering gear ratio thereof is decided by adding a proportional factor depending on the steering angle and the differential factor as mentioned above.
However, according to the front-wheel steering control apparatus which corrects a steering angle only by the vehicle speed and an operation of the driver as disclosed in the above mentioned prior art, there arises a problem that it is difficult to improve a yaw response of the vehicle in association with sufficiently suppressing an unstable vehicle behavior due to a resonance of a yaw movement of steering controls.